Apparatus for determining at least one evaluation parameter of a blood sample

ABSTRACT

The present invention provides a method for determining at least one evaluation parameter of a blood sample, comprising the following steps: providing (S 4 ) at least one blood gas parameter; providing (S 5 ) at least one hemostasis parameter; and determining (S 6  . . . S 10 ″) the at least one evaluation parameter as a function of the blood gas parameter and/or the hemostasis parameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 12/764,611 filed Apr. 21, 2010, which claims thebenefit of European patent application No. 10 157 562.9 filed Mar. 24,2010, the entire disclosures of which are herein incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for determiningat least one evaluation parameter of a blood sample.

BACKGROUND OF THE INVENTION

During the perioperative period, the anesthetist has to monitor, controland interpret a great number of factors having an influence on thepatient's well being. These factors are, in particular, hemostasis,oxygenation, nutrition, ph-level and body temperature. Further, theanesthetist must evaluate the influence of a blood product beingtransfused to a patient who has suffered a severe loss of blood.

Hemostasis is the process by which bleeding from a damaged blood vesselstops. It is a dynamic, extremely complex process involving manyinteracting factors, which include coagulation, i.e. the process bywhich blood clots are formed, fibrinolytic proteins, activators,inhibitors and cellular elements. Since none of these factors remainsstatic or works in isolation, it is necessary to measure continuouslyall phases of a patient's hemostasis as a net product of all bloodcomponents in a non-isolated and non-static fashion.

Furthermore, it is well known that coagulopathy is sometimes confusedwith hypothermia, acidosis and preexisting disorders like morbid ionizedcalcium concentration. For example:

-   -   Trauma patients are prone to hypothermia, which slows down        enzymatic reactions, modifies platelet function, decreases        platelet counts and stimulates fibrinolysis.    -   Acidosis worsens fibrin polymerization and strengthening of the        clot.    -   Low ionizied calcium concentration (as the result of a massive        PRBC transfusions containing citrate) and a low hematocrit        (<30%) further aggravate bleeding diathesis.    -   Increased base deficit (BD) or decreased base excess (BE),        respectively, are known to influence the haemostatic potential.

Various methods have been introduced to assess hemostasis parameterslike the potential of blood to form an adequate clot. Common laboratorytests such as thrombocyte counts or the determination of fibrinconcentration provide information on whether the tested component isavailable in sufficient amount but lack in answering the questionwhether the tested component works properly under physiologicalconditions (e.g. the activity of fibrinogen under physiologicalconditions cannot be accessed by common optical methods).

A group of tests which overcomes these problems is summarized by theterm “viscoelastic methods”. The common feature of these methods is thatthe blood clot firmness (or other parameters dependent thereon) iscontinuously determined, from the formation of the first fibrin fibresuntil the dissolution of the blood clot by fibrinolysis. Blood clotfirmness is a functional parameter, which is important for hemostasis invivo, as a clot must resist blood pressure and shear stress at the siteof vascular injury. Clot firmness results from multiple interlinkedprocesses: coagulation activation, thrombin formation, fibrin formationand polymerization, platelet activation and fibrin-platelet interactionand can be compromised by fibrinolysis. Thus, by the use of viscoelasticmonitoring all these mechanisms of the coagulation system can beassessed.

The first viscoelastic method was called “thromboelastography” (HartertH: Blutgerinnungsstudien mit der Thromboelastographie, einem neuenUntersuchungsverfahren. Klin Wochenschrift 26:577-583, 1948). In thethromboelastography, the sample is placed in a cup that is periodicallyrotated to the left and to the right by about 5°, respectively. A pin isfreely suspended by a torsion wire. When a clot is formed it starts totransfer the movement of the cup to the pin against the reverse momentumof the torsion wire. The movement of the pin as a measure for the clotfirmness is continuously recorded and plotted against time. Forhistorical reasons the firmness is measured in millimeters.

One of the most important parameters determined by thromboelastographyis the time between the activator induced start of the coagulationcascade and the time until the first long fibrin fibres have been builtup which is indicated by the firmness signal exceeding a defined value.This parameter will be called clotting time in the following. Anotherimportant parameter is the clot formation time which gives a measure forthe velocity of the development of a clot. The clot formation time isdefined as the time it takes for the clot firmness to increase from 2 to20 mm. The maximum firmness a clot reaches during a measurement, furtheron referred to as maximum clot firmness or just MCF, is also of greatdiagnostic importance.

Modifications of the original thromboelastography technique (Hartert etal. (U.S. Pat. No. 3,714,815) have been described by Cavallari et al.(U.S. Pat. No. 4,193,293), by Do et al. (U.S. Pat. No. 4,148,216), byCohen (U.S. Pat. No. 6,537,819), further modifications by Calatzis etal. (U.S. Pat. No. 5,777,215) are called thromboelastometry.

Besides hemostasis, parameters like oxygenation, nutrition and ph-levelneed to be analyzed by the anesthetist. It is commonly known to useblood gas analyzers as described in EP 1 367 392 A1 for this purpose.Blood gas analyzers generally measure the partial pressures of certaingases in a blood sample and other parameters like ph-level andhematocrit. From these partial pressures oxygenation and other factorscan be deduced. Devices known as clinical chemistry analyzers are alsoavailable in the market. These devices are also used to determine someof the parameters determined by blood gas analyzers. When it is referredto blood gas analyzers henceforth, this is also to include clinicalchemistry analyzers and electrolyte analyzers. Further, when it isreferred to blood gas parameters henceforth, this is also to includeclinical chemistry parameters and electrolyte parameters.

Further, in current practice blood products are usually prepared andapplied according to fixed protocols independently from any individualproperties of the initial donor or other influences (e.g., storageduration, storage conditions, etc.). In particular, their potential tointeract with other factors like the patient's oxygenation, ph-level orhemostasis are not assessed prior to application of the blood productsnowadays.

Monitoring, controlling and interpreting this great number of factors aswell as their interdependence, especially in stressful environments likeoperation theaters, put great pressure on the anesthetist. This pressuremay result in mistakes with severe consequences for the patient.

It is therefore an object of the present invention to support theanesthetist and/or provide the anesthetist with information in a betterway.

SUMMARY OF THE INVENTION

Accordingly, a method for determining at least one evaluation parameterof a blood sample is provided, the method comprising the followingsteps: providing at least one blood gas parameter; providing at leastone hemostasis parameter; and determining the at least one evaluationparameter as a function of the blood gas parameter and the hemostasisparameter.

Furthermore, an apparatus for determining at least one evaluationparameter of a blood sample is provided, in particular for performingthe method according to the invention, the apparatus comprising: a bloodgas unit for providing at least one blood gas parameter; a hemostasisunit for providing at least one hemostasis parameter; and a evaluationunit for determining the at least one evaluation parameter as a functionof the blood gas parameter and the hemostasis parameter.

Furthermore, a computer program being adapted to perform the methodaccording to the invention on a computer is provided.

Furthermore, a data carrier which stores a computer program according tothe invention is provided.

The at least one evaluation parameter that is determined as a functionof the blood gas parameter and the hemostasis parameter can be providedto the anesthetist in one or another way to simplify his decision makingprocess, or even obviate the same. Alternatively or additionally, theevaluation parameter can be used to verify the anesthetist's decisionmaking process, thus making it more safe. Of course, the evaluationparameter may also be provided to another device that performs afunction related to anesthetics, for example. Such a device may be acardiopulmonary bypass device.

Preferred embodiments are given in the dependent claims.

Herein, a “blood sample” refers to a whole blood sample and/or a samplecontaining blood components, e.g. a blood plasma sample.

According to a preferred embodiment of the method of the presentinvention the step of providing the blood gas parameter comprises atleast one of the following steps: performing a blood gas analysis,measuring the blood gas parameter, reading out a sensor, reading out adata input device and/or reading out a data storage. The blood gasanalysis may be preformed using a blood gas analyzer as described above.The sensor may be a keyboard, for example, that the anesthetist uses toenter the blood gas parameter.

According to a further preferred embodiment of the method of the presentinvention the blood gas parameter is selected from and/or is a functionof at least one of a group of parameters, the group comprising: apartial pressure of carbon dioxide, a partial pressure of oxygen, apartial pressure of nitrogen oxide, a pH-level, a base excess, a basedeficit, hematocrit, a bicarbonate level, a concentration of lactate, aconcentration of electrolytes, in particular calcium ions, aconcentration of hemoglobin, a concentration of oxyhemoglobin, aconcentration of carboxyhemoglobin and/or a concentration ofmethemoglobin.

According to a further preferred embodiment of the method of the presentinvention the step of providing the hemostasis parameter comprises atleast a one of the following steps: performing a hemostasis analysis,measuring the hemostasis parameter, reading out a sensor, reading out adata input device and/or reading out a data storage. The hemostasisanalysis may be preformed using any one of the methods as describedabove, for example a viscoelastic method, in particularthromboelastography. Traditional methods like thrombocyte count may alsobe used. The sensor may be a keyboard, for example, that the anesthetistuses to enter the hemostasis parameter. The data storage may be part ofthe evaluation unit for determining the at least one evaluationparameter as a function of the blood gas parameter and the hemostasisparameter or it may be part of the hemostasis unit, e.g. athromboelastometer.

According to a further preferred embodiment of the method of the presentinvention the hemostasis parameter is a coagulation parameter or a clotlysis parameter. Whereas hemostasis describes the entire process bywhich bleeding from a damaged blood vessel stops, coagulation onlyrefers to the process of forming blood clots. “Lysis” refers to theprocess by which a blood clot is dissolved, i.e. the opposite ofcoagulation. Lysis is basically initiated by the activity of plasmin. Anexample for a clot lysis parameter is the decrease in clot firmness inrelation to the maximum clot firmness or the plasmin level.

According to a further preferred embodiment of the method of the presentinvention the coagulation parameter is selected from and/or is afunction of at least one of a group of parameters, the group comprising:a clotting time, a clot formation time, a clot firmness, a maximum clotfirmness, a fibrinogen functionality, a platelet functionality, aninhibitor functionality, in particular a protein C-level, a tissuefactor passway inhibitor (TFPI)-level or an ATIII-level, and/or sampleviscosity. An example for a fibrinogen functionality is the clotfirmness or maximum clot firmness of a viscoelastic measurement of ablood sample in the presence of a platelet inhibitor. An example for aplatelet functionality is the difference of the clot firmnesses ormaximum clot firmnesses of a viscoelastic measurement of a blood samplein the absence and in the presence of a platelet inhibitor. Anotherexample of the platelet functionality is the aggregation behavior of theblood sample in the presence of a platelet activator, e.g. measured byoptical or electrical means.

According to a further preferred embodiment of the method of the presentinvention it comprises the steps of: providing a temperature parameterof the blood sample, a temperature parameter of a patient's body and/oran expected temperature parameter of a patient's body and determiningthe evaluation parameter also as a function of the temperature parameterand/or expected temperature parameter. When it is referred to atemperature parameter henceforth, this is also to include an expectedtemperature parameter, preferably. For example, patients are typicallycooled down during heart operations. The temperature of the blood sampletaken from such a patient may be much lower than normal having a directinfluence on blood gas analysis as well as hemostasis analysis. Forexample, the low temperature will result in a high oxygen saturation ofthe blood sample, thereby changing the partial pressure of oxygen, i.e.a typical blood gas parameter, measured in blood gas analysis. Further,the low temperature may result in significantly prolonged clottingtimes. By taking the patient's expected temperature into account bloodgas parameters and/or hemostasis parameters can be corrected accordinglyin order to properly assess the patient's condition when he is at theexpected temperature, e.g. just before he wakes up from anesthesia. Onthe other hand, the blood sample, being cool initially, warms up untilblood gas analysis as well as hemostasis analysis is completed. Again,by taking the patient's temperature into account, blood gas parametersand/or hemostasis parameters can be corrected to the patient's actualtemperature in order to correctly assess hemostasis at the patient'sactual temperature.

According to a further preferred embodiment of the method of the presentinvention the step of providing the temperature parameter comprises atleast a one of the following steps: measuring the temperature parameter,reading out a sensor, reading out a data input device and/or reading outa data storage. A thermometer connected to the patient is one example ofa suitable sensor. The input device may be a keyboard, for example, usedby the anesthetist to enter the patient's temperature manually.

According to a further preferred embodiment of the method of the presentinvention the step of determining the evaluation parameter comprises atleast one of the following steps: comparing the blood gas parameter witha blood gas parameter range and/or comparing the blood gas parameterwith a blood gas parameter value. These blood gas parameter ranges orvalues are typically determined up front or can be found in the relevantliterature and may be provided in the form of tables in electronicformat to carry out the step of comparing. By way of this comparison, itcan, for example, be determined if a blood gas parameter is inside anallowable range which will ensure that the hemostasis parametersobtained are meaningful.

According to a further preferred embodiment of the method of the presentinvention the step of determining the evaluation parameter comprises atleast one of the following steps: comparing the temperature parameterwith a temperature parameter range and/or comparing the temperatureparameter with a temperature parameter value. These temperatureparameter ranges or values (which may include expected temperatureranges or values) are typically determined up front or can be found inthe relevant literature and may be provided in the form of tables inelectronic format to carry out the step of comparing. By way of thiscomparison, it can, for example, be determined if the temperatureparameter is inside an allowable range which will ensure that thehemostasis parameters obtained are meaningful.

According to a further preferred embodiment of the method of the presentinvention it further comprises the step of providing an interdependenceparameter describing an interdependence between at least two of a groupof parameters, the group comprising: the blood gas parameter, thehemostasis parameter and the temperature parameter. As outlined abovesome blood gas parameters and/or hemostasis parameters are dependent ontemperature. However, others are not, or not to a relevant extent. Theinterdependence parameter may only describe if there is a dependence ornot. However, the interdependence may also describe the degree ofdependence. These dependence parameters are typically determined upfront or can be found in the relevant literature and may be provided inthe form of tables in electronic format to carry out the step ofproviding.

According to a further preferred embodiment of the method of the presentinvention the blood gas parameter range, the blood gas parameter value,the temperature parameter range, the temperature parameter value and/orthe interdependence parameter is provided by means of calculating,estimating, measuring, reading out a sensor, reading out a data inputdevice and/or reading out a data storage.

According to a further preferred embodiment of the method of the presentinvention the step of comparing the blood gas parameter with a blood gasparameter range and/or comparing the blood gas parameter with a bloodgas parameter value is performed as a function of the interdependenceparameter. For example, if according to an interdependence parameter aspecific hemostasis parameter, for example the clotting time, isdependent on a blood gas parameter, for example pH-value, then only willthe blood gas parameter be compared to the blood gas parameter range orvalue. Otherwise, this comparison shall not be carried out to ensure anefficient process.

According to a further preferred embodiment of the method of the presentinvention the step of comparing the temperature parameter with atemperature parameter range and/or comparing the temperature parameterwith a temperature parameter value is performed as a function of theinterdependence parameter. For example, if according to aninterdependence parameter a specific hemostasis parameter, for examplethe clotting time, is dependent on a temperature parameter, for examplethe temperature of the blood sample, then only will the temperatureparameter be compared to the temperature parameter range or value.Otherwise, this comparison shall not be carried out to ensure anefficient process.

According to a further preferred embodiment of the method of the presentinvention the hemostasis parameter is corrected as a function of theblood gas parameter and/or temperature parameter. For example, if ablood gas parameter and/or temperature parameter is not within itsallowable range, the hemostasis can be corrected accordingly. Hence,adjusting of the blood gas parameter and/or temperature parameter upfront, e.g. by chemical/biological means, can be avoided, thus ensuringan efficient process.

According to a further preferred embodiment of the method of the presentinvention the blood gas parameter is corrected as a function of thehemostasis parameter and/or temperature parameter. It is preferred toadapt the hemostasis parameter as a function of the blood gas parameter.However, in some instances it may be preferable to do it the other wayaround. Possibly, the hemostasis parameter and the blood gas parameterboth depend on temperature which may require adapting both parameters.

According to a further preferred embodiment of the method of the presentinvention the hemostasis parameter, corrected hemostasis parameter,blood gas parameter and/or corrected blood gas parameter is transmittedto a data output device and/or output by a data output device as afunction of the determined evaluation parameter. For example, if it isindicated by the interdependence parameter that the hemostasis parameteris not dependent on the blood gas parameter, then the evaluationparameter is set to equal 1 (Boolean). When the evaluation parameterequals 1, then the hemostasis parameter is displayed on an outputdevice, e.g. a computer screen, to the anesthetist. Otherwise, if theinterdependence parameter shows that the hemostasis parameter isdependent on the blood gas parameter and it is found that the blood gasparameter is out of its allowable range, then the evaluation parameteris set to 0. When the evaluation parameter equals 0, then the hemostasisvalue is not displayed on the output device.

According to a further preferred embodiment of the method of the presentinvention the evaluation parameter is transmitted to a data outputdevice and/or output by a data output device. By another example, if theinterdependence parameter shows that the hemostasis parameter isdependent on the blood gas parameter and it is found that the blood gasparameter is out of its allowable range, then the hemostasis value isdisplayed on the output device; however, the evaluation parameter is setto the message “Blood gas parameter out of range” which is displayed onthe screen.

According to a further preferred embodiment of the method of the presentinvention an output information and/or a control command for the dataoutput device is selected from a plurality of output information and/orcontrol commands as a function of the determined evaluation parameter.By another example, if the interdependence parameter shows that thehemostasis parameter is dependent on the blood gas parameter and it isfound that the blood gas parameter is out of its allowable range, thenthe hemostasis value is displayed on the output device. The evaluationparameter may depend on the specific type of blood gas parameter beingout of range. Then, depending on the evaluation parameter an outputinformation, e.g. a message saying “pH-level out of range”, is selectedfrom a plurality of output information, e.g. a table of messages“pH-level out of range”, “partial pressure of oxygen out of range” etc.and displayed on the screen along with the hemostasis parameter.

According to a further preferred embodiment of the method of the presentinvention the steps of providing the blood gas parameter and thehemostasis parameter comprise the step of analyzing the same sample ordifferent samples of blood. Analyzing only one sample can be moreefficient though.

According to a further preferred embodiment of the method of the presentinvention the step of analyzing the same sample of blood comprises thestep of proving the same sample or different samples of blood withoutadditives. For example, when the period of time between taking the bloodsample of the patient and performing the blood gas analysis and/or thehemostasis is small it may be advantageous to not add any additivesbecause the time for substantial coagulation to take place is small.Without additives being added to the blood more accurate measurements ofthe blood gas parameter and/or the hemostasis parameter may be possible.

According to a further preferred embodiment of the method of the presentinvention the step of analyzing the same sample or different samples ofblood comprises the step of adding inhibitors and/or antagonists. Theinhibitor, e.g. heparin, may be required to prevent coagulation whilstmeasuring the blood gas parameter, e.g. pH-level. Thereafter, whenmeasuring the hemostasis parameter, e.g. clot firmness, in the sameblood sample, heparin may be detrimental. Therefore, an antagonist isadded, e.g. protamin, which will allow the blood to clot again.

According to a further preferred embodiment of the method of the presentinvention the blood sample is taken from the patient at the point ofcare or from a blood product. Herein, a blood product means whole bloodor any component, e.g. red blood cells, blood plasma, or platelets, ofblood which is collected from a donor for use in a blood transfusion.

According to a further preferred embodiment of the method of the presentinvention a blood sampling time, blood sample identifier and/or patientidentifier is assigned to the blood gas parameter, hemostasis parameter,temperature parameter and/or evaluation parameter. For example, theblood gas parameter, the blood sampling time, i.e. the point in timethat the blood sample was taken, and the blood sample identifier, i.e. aunique code which is, e.g., associated with the patient or bloodproduct, is electronically stored together in the same matrix togetherwith the blood gas parameter, hemostasis parameter, temperatureparameter and/or evaluation parameter.

According to a further preferred embodiment of the apparatus of thepresent invention it further comprises a temperature unit for providinga temperature parameter of the blood sample, a temperature parameter ofa patient's body and/or an expected temperature parameter of a patient'sbody, wherein the evaluation unit determines the evaluation parameteralso as a function of the temperature parameter and/or expectedtemperature parameter. Providing and using a temperature parameter indetermining the evaluation parameter may be advantageous as alreadyoutlined above.

According to a further preferred embodiment of the apparatus of thepresent invention at least one the blood gas unit, hemostasis unit,evaluation unit and/or temperature unit is selected from a group, thegroup comprising: a technical device, a computer system, a server, aclient and a mobile device.

Typically, the blood gas unit is a blood gas analyzer.

Typically, the hemostasis unit is a hemostasis analyzer, in particular arheometric or viscoelastic measurement unit. An example for aviscoelastic measurement unit is a thromboelastometer or athrombelastograph.

Typically, the temperature unit is a thermometer, in particular athermometer in direct contact with the patient or a remotely sensingthermometer.

According to a further preferred embodiment of the apparatus of thepresent invention the blood gas unit, the hemostasis unit, theevaluation unit and/or the temperature unit are integrated into a singlehousing. This may be space and resource efficient.

According to a further preferred embodiment of the apparatus of thepresent invention it has a single cartridge for receiving the bloodsample. Thus, the same blood sample is used for measuring the blood gasparameter, hemostasis parameter and/or temperature parameter.

According to a further preferred embodiment of the apparatus of thepresent invention it has a single cartridge for receiving two differentblood samples. Thus, two different blood samples are used for measuringthe blood gas parameter, hemostasis parameter and/or temperatureparameter. The two samples may differ with respect to the additives ineach blood sample, e.g. different coagulation inhibitors may have beenadded to the two blood samples.

According to a further preferred embodiment of the apparatus of thepresent invention a temperature of the blood gas unit and/or thehemostasis unit is controlled as a function of the temperatureparameter. For example, it may be useful for the blood gas unit and/orthe hemostasis unit to be at the patient's temperature thus allowing toproperly assess the patient's actual condition.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the subsequent description and the appended claims,taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a preferred embodiment of an apparatusin accordance with the present invention;

FIG. 2 is a schematic diagram of another preferred embodiment of anapparatus in accordance with the present invention;

FIG. 3 is a flow chart illustrating a preferred embodiment of a methodin accordance with the present invention;

FIG. 4 is a diagram showing clot formation time vs. temperature for twodifferent pH levels; and

FIG. 5 is a diagram showing clotting time vs. temperature for twodifferent pH levels;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the figures like reference numerals designate like or functionallyequivalent elements unless otherwise indicated.

FIG. 1 shows an apparatus 1 having an hemostasis unit 2, a blood gasunit 3 and an evaluation unit 4.

The hemostasis unit 2 provides an hemostasis parameter to the evaluationunit 4 as indicated by the dotted line in FIG. 1. The hemostasis unit 2is formed as a thromboelastometer, for example as described in U.S. Pat.No. 5,777,215. Typical hemostasis parameters that may be determinedusing the thromboelastometer 2 are clotting time and clot formation timeas defined in the introduction. To this end, a blood sample is takenfrom a patient 5—as indicated by the dashed line in FIG. 1—and analyzedin the thromboelastometer 2. The thromboelastometer 2 has a datainterface by which the hemostasis parameter can be transmitted to theevaluation unit 4.

As an alternative, the hemostasis unit 2 may be formed as a keyboard forthe anesthetist to enter the hemostasis parameter manually.

The blood gas unit 3 provides a blood gas parameter to the evaluationunit 4 as indicated by the dotted line in FIG. 1. The blood gas unit 3is formed as a blood gas analyzer, for example as described in EP 1 367392 A1. Typical blood gas parameters that may be determined using theblood gas analyzer 3 are pH-level and the partial pressure of oxygen. Tothis end, another blood sample is taken from the patient 5—as indicatedby the dashed line in FIG. 1—and analyzed in the blood gas analyzer 3.The blood gas analyzer 3 has a data interface by which the blood gasparameter can be transmitted to the evaluation unit 4.

As an alternative, the blood gas unit 3 may be formed as a keyboard forthe anesthetist to enter the blood gas parameter manually.

The evaluation unit determines at least one evaluation parameter as afunction of the blood gas parameter and the hemostasis parameter. Theevaluation parameter will support the anesthetist in his diagnosis ofthe patient's condition as explained in more detail with reference toFIG. 3. This support may lie in reducing the complexity of the data theanesthetist has to deal with. Additionally or alternatively, theevaluation parameter may be used to verify data and/or the anesthetist'sdecision making process. The evaluation unit is formed as a computer.

The blood sample may also be taken from a blood product to be transfusedto the patient 5.

The apparatus 1 may further comprise a temperature unit 6. Thetemperature unit 6 provides a temperature parameter to the evaluationunit 4 as indicated by the dotted line in FIG. 1.

The temperature unit 6 is formed as a thermometer measuring—as indicatedby the dashed-and-dotted line—the temperature parameter, for example thepatient's temperature. The thermometer 6 has a data interface by whichthe temperature parameter can be transmitted to the evaluation unit 4.The evaluation unit 4 determines the evaluation parameter also as afunction of the temperature parameter.

As an alternative, the temperature unit 6 may be formed as a keyboardfor the anesthetist to enter the temperature parameter manually. Thismay be the patient's actual temperature or his expected temperature, forexample.

Of course, numerous arrangements are conceivable: for instance, theevaluation unit 4 may be physically integrated into the hemostasis unit2 or the blood gas analyzer 3.

The apparatus 1 may further include an output device 7, e.g. a screen,for displaying the evaluation parameter to the anesthetist. To this end,the screen 7 has a data interface to the evaluation unit 4 indicated bythe dotted line in FIG. 1.

FIG. 2 shows the apparatus 1 of FIG. 1. However, in the apparatusaccording to FIG. 2, the hemostasis unit 2, the blood gas unit 3 and thetemperature unit 4 are integrated into a single housing 10 (except for atemperature sensor that is not shown in FIG. 2). Preferably, the logicfor the hemostasis unit 2, the blood gas unit 3 and the temperature unit4 are integrated onto the same circuit board or even onto the same chip11.

Further, the apparatus 1 of FIG. 2 comprises two cartridges 12, 13 forblood samples. Cartridge 12 is used by the hemostasis unit 2 todetermine the hemostasis parameter. Cartridge 13 is used by the bloodgas unit 3 to determine the blood gas parameter.

If the period of time between taking the blood samples of the patientand determining the hemostasis parameter/blood gas parameter is short,e.g. smaller than approximately 15 minutes, it is preferred to analyzethe blood samples as is, i.e. without additives like e.g. heparin, inthe cartridges 12, 13. However, if the period of time is substantiallylonger than 15 minutes, it is preferred to add an inhibitor like heparinto the blood samples immediately after taking the blood sample from thepatient. This will prevent the blood from coagulating. Yet, in order tomeasure hemostasis parameters like clotting time it may be necessary toremove the inhibitor. This can be done by adding an antagonist, e.g.protamin, to the blood sample set up for measuring the hemostasisparameter.

According to the embodiment of FIG. 2, the temperature unit measures notonly the temperature of the patient but also the temperature of eachblood sample in the cartridges 12, 13.

Rather than having two cartridges 12, 13, only a single cartridge may beused. The hemostasis parameter and blood gas parameter may then bemeasured in different sectors of the blood sample.

With reference to FIG. 3, a preferred embodiment of a method inaccordance with the present invention is explained. The method may beperformed by the apparatuses of FIGS. 1 and 2.

Initially, a blood sample is taken from a patient or a blood product(step S1).

The temperature of the blood sample is controlled (step S3) by asuitable heating and/or cooling device which may be part of theapparatus 1. For example, a patient is cooled down for heart surgery.Then, it may be advisable to bring the blood samples temperature to thepatient's temperature since the temperature of the blood sample maychange once it is taken from the patient, when it is desired to analyzethe patient's current situation with regard to coagulation, for example.To this end, the patient's temperature is measured in the foregoing step(step S2). Or, the temperature of the blood sample is brought to normaltemperature (37° Celsius) in order to simulate the patient's conditionon waking up.

According to a further embodiment, the temperature of the blood sampleis not controlled but an expected temperature is provided by theanesthetist, e.g. by entering the same via the temperature unit 6.

Thereafter, a blood gas parameter of the blood sample, e.g. pH, isdetermined (step S4). Before, parallel to, or after step 4, a hemostasisparameter of the blood sample, e.g. clotting time and/or clot formationtime, is determined (step S5).

In step S6, it is determined if the hemostasis parameter is a functionof the blood gas parameter. To this end, an interdependence parameterfor the blood gas parameter and hemostasis parameter at the measured orexpected temperature (temperature parameter) is read from a datastorage, which may be part of the apparatus 1. The interdependenceparameter may be stored electronically in a table of the following form:

temperature blood gas hemostasis parameter interdependence parameterparameter (° Celsius) parameter pH clot formation time 30-33 Yes pH clotformation time 36-39 No pH clotting time 30-33 No pH clotting time 36-39No partial pressure of . . . . . . . . . oxygen

The interdependence parameter can be determined in experiments up frontlike the one shown in FIGS. 4 and 5.

FIG. 4 shows the relationship between clot formation time and pH levelfor different temperatures. FIG. 5 shows the same relationship forclotting time. As can be gathered from FIGS. 4 and 5, there is nosubstantial interdependence between clotting time/clot formation timeand pH levels at a temperature of 36-39° Celsius. However, there is astrong interdependence between clot formation time and pH levels of7.0-7.3 at a temperature of 30-33° Celsius.

If it is determined that the hemostasis parameter is not a function ofthe blood gas parameter, then the hemostasis parameter is displayed on ascreen to the anesthetist in Step S7. Seeing the hemostasis parameterbeing displayed, the anesthetist knows that the hemostasis parameter hasbeen determined accurately. He or a further device can now analyze thehemostasis parameter with regard to disorders, e.g. coagulopathy, instep S8.

Step S6 increases efficiency but is optional.

Otherwise, i.e. if the hemostasis parameter is a function of the bloodgas parameter, it is determined if the blood gas parameter is allowable.E.g. a pH-level of smaller than 7.0 will not allow for reliablemeasurements of clotting time. To this end, allowable ranges of theblood gas parameter are read from a data storage, which may be part ofthe apparatus 1. The allowable ranges may be stored electronically in atable of the following form:

blood gas parameter allowable range pH 7.0 < pH < 7.4 partial pressureof oxygen . . .

Of course, the table may also include the temperature parameter.

Hence in step S9, the blood gas parameter is compared to its allowablerange. If it is within its allowable range, step 7 follows.

In addition or as an alternative, step 9 may also be performed withrespect to the temperature parameter to ensure that the temperatureparameter is within its allowable range for a specific hemostasisparameter.

If the blood gas parameter is not within its allowable range, accordingto one embodiment, the hemostasis parameter will be displayed on thescreen accompanied by a warning “pH value out of range” (step S10). Itis then up to the anesthetist to adjust the pH-level in the bloodsample. In this case, the evaluation parameter is comprised of thehemostasis parameter being displayed/the warning being displayed alongwith hemostasis parameter.

According to an alternative embodiment, the hemostasis parameter is notdisplayed on the screen but a warning “pH value out of range” (stepS10′). It is then up to the anesthetist to adjust the pH-level in theblood sample. By not displaying the hemostasis parameter, it is ensuredthat the anesthetist will only continue with step S8 once the hemostasisparameter is correct. In this case, the evaluation parameter iscomprised of displaying/not displaying the hemostasis parameter.

If a plurality of hemostasis parameters are being determined, it may beuseful to apply step S10′ to each hemostasis parameter individually,i.e. only the hemostasis parameters which are incorrect are not beingdisplayed, whereas the correct hemostasis parameters are displayed andcan be used by the anesthetist. However, a more simple method could bedesigned such as to display none of the hemostasis parameters if one ofthem shows to be incorrect.

According to a further alternative embodiment, the hemostasis parameteris automatically corrected to make up for the blood parameter and/ortemperature parameter not being inside its allowable range (Step 10′).This correction may be based on experimental data, stored in formulaeand/or in tables on an electronic storage device, which may also be partof the apparatus 1. After correction of the hemostasis, the methodcontinues at step S7. In this case, the evaluation parameter iscomprised of the corrected hemostasis parameter being determined anddisplayed.

The steps S3 and S6-S10″ are performed by the evaluation unit 4 of theapparatus 1. Step S4 is performed by the blood gas unit 3 and step S5 bythe hemostasis unit 2 of the apparatus 1.

Although the present invention has been described in accordance withpreferred embodiments, it is obvious for a person skilled in the artthat modifications are possible in all embodiments.

Of course the invention is not limited to be used by anesthetists butcan be used by any medical practitioner, in particular.

What is claimed is:
 1. An apparatus for determining at least oneevaluation parameter of a blood sample, comprising: a blood gas analyzerconfigured to determine at least one blood gas parameter of the bloodsample from the group of pH level and partial pressure of oxygen; athromboelastometer configured to determine at least one hemostasisparameter of the blood sample from the group of blood clotting time andblood clot formation time; and an evaluation unit coupled to thethromboelastometer via a first data interface, coupled to the blood gasanalyzer via a second data interface and configured to determine the atleast one evaluation parameter as a function of the blood gas parameterand the hemostasis parameter, the evaluation unit comprising aprocessor; wherein the processor is programmed to determine the at leastone evaluation parameter of at least one blood sample by carrying outcomputer-executable instructions on in a non-transitorycomputer-readable medium for performing steps comprising: providing theat least one blood gas parameter; providing the at least one hemostasisparameter; providing an interdependence parameter describing aninterdependence between the blood gas parameter and the hemostasisparameter; and determining the at least one evaluation parameter as afunction of the blood gas parameter and the hemostasis parameter;wherein determining the evaluation parameter comprises at least one ofthe following: comparing the blood gas parameter with a blood gasparameter range and/or comparing the blood gas parameter with a bloodgas parameter value; wherein comparing the blood gas parameter with ablood gas parameter range and/or comparing the blood gas parameter witha blood gas parameter value is performed as a function of theinterdependence parameter; and wherein the interdependence parameter isprovided by reading out a sensor, reading out a data input device and/orreading out a data storage.
 2. The apparatus according to claim 1,further comprising a single cartridge for the blood sample.
 3. Theapparatus according to claim 1, wherein a temperature of the blood gasanalyzer and/or the thromboelastometer is controlled as a function of atemperature parameter of the blood sample determined by a thermometer.